Field of the Invention and Related Art
The present invention relates to a photosensitive composition, particularly a photosensitive composition used as a resist composition, a method for patterning using the same, and a method for manufacturing a semiconductor device.
A method for forming fine patterns in conventional manufacturing processes of semiconductor devices is described in "Silicon-Added Bilayer Resist (SABRE) System, W. C. McColgine, et, al. SPIE. Vol. 920, pp.260-267 (1988)", for example. The method will be explained with reference to FIGS. 1A to 1D.
As shown FIG. 1A, a resist, e.g. a polyimide resist, is applied onto a semiconductor substrate 4 to form an underlying resist film 3, and then an i-line sensitive resist is applied thereon to form an overlay resist film 2 (hereinafter the combination of the semiconductor substrate 4 and resist films 2 and 3 is called "integral article"). Ultraviolet light, for example, having the i-line wavelength (365 nm) is irradiated to the overlay resist film 2 through a given mask (not shown in the figure) to expose the overlay resist film 2 to the i-line 1. A developed pattern 5 as shown in FIG. 1B is formed by developing the overlay resist film 2. Next, the integral article is exposed to vapor of a sililation agent 6, e.g. hexamethyldisilazane while heating as shown in FIG. 1C. Only the developed pattern 5 is sililated thereby to form a sililated layer 7 on the underlying resist film 3. Then, as shown in FIG. 1D, the underlying resist film 3 is etched by oxygen reactive ion etching (RIE) with an etching mask of sililated layer 7 to form a fine pattern. In FIG. 1D, the resulting SiO.sub.2 layer 9 is formed by oxygen plasma 8.
The method for forming a fine pattern set forth above has the following problems:
Dry etching of the underlying resist film 3 is unavoidable to transfer the developed pattern formed in the overlay resist film 2 to the underlying resist film 3. Therefore, an exclusive etcher for organic film must be employed, and the process requires complicated optimization to improve planar uniformity and selective or etching ratio.
In particular, when a general etcher for organic film is used for etching in the transfer of the fine developed pattern in the overlay resist film 2 to the thick underlying resist film 3 (for example, 1.5 .mu.m thick), a vertical pattern is barely formed. In detail, because the general etcher for organic film has a strong reactivity, the underlying resist film is isotropically etched and undercut. Therefore, an etcher exhibiting a high anisotropic etching characteristic is required for transferring the fine developed pattern in the overlay resist film 2 to the underlying resist film 3.
Further, significantly complicated process optimization is required for the selection of etching gas, the mixing ratio of a plurality of gasses, gas pressure, temperature, Rf bias, extraction voltage bias, and Rf frequency.